The attack happened on Thursday in the town of Ldaoussaf in a region troubled by jihadist insurgents, the two sources told AFP, speaking on condition of anonymity.

"An army patrol was ambushed," a senior army officer said, adding that a soldier had been killed and another injured.

"The assailants fled with weapons."

A local authority representative who also wanted to remain anonymous confirmed the toll.

The Far North is a tongue of land that lies between Nigeria to the west and Chad to the east.

Nigeria's Boko Haram and its dissident branch, the Islamic State in West Africa Province (ISWAP), have in recent years carried out deadly attacks against security forces and civilians in northern Cameroon, as well as adjacent parts of Nigeria, Niger and Chad.

Boko Haram launched an insurgency in northeast Nigeria in 2009 before it spread through the region.

More than 36,000 people have been killed since, mainly in Nigeria, and three million forced to flee their homes, the United Nations says.